/**
  * @see EPSInterface::addParcel()
  */
 public function addParcel($sessionId, $parcel)
 {
     try {
         $addParcelStdObject = new stdClass();
         $addParcelStdObject->sessionId = $sessionId;
         $addParcelStdObject->parcel = $parcel->toStdClass();
         $response = parent::addParcel($addParcelStdObject);
         if (isset($response->return)) {
             $result = $response->return;
         } else {
             $result = null;
         }
         return $result;
     } catch (SoapFault $sf) {
         throw new ServerException($sf);
     }
 }